In known aircraft cooling systems, conditioned supply air to an aircraft cabin is recirculated and mixed with cooled sub-freezing air from an air conditioning pack via a mix manifold and ductwork system. The recirculated air may be passed through a heat exchanger that cools and condenses moisture from the air to a recirculation duct and on to the mix manifold. The recirculation duct may be tied into the top of a pack duct that directs sub-freezing air from an air conditioning pack to the mix manifold. In these systems, the condensate from the recirculation duct may drain into the pack duct and freeze. As the frozen condensate builds in the pack duct, air flow may become obstructed.